Crop-drying oil burner

ABSTRACT

Disclosed is a crop-drying oil burner particularly adapted to be used outdoors when ambient temperatures are below about 45* F. This burner includes an inner cylindrical combustion chamber, and a concentric outer air chamber spaced from the inner chamber and including a spaced front plate which covers the open front end of the inner chamber. This front plate has a circular orifice therein which allows flame to shoot out of the inner chamber. High-velocity air is blown through the inner chamber and through the gap between the inner and outer chambers, sweeping across the front plates&#39;&#39; inside surface, keeping it free of carbon.

United States Patent [72] lnventor Donald C. Walker Munster, Ind. [21] AppL-No 855,861 [22] Filed Sept. 8, 1969 [45] Patented Aug. 3, 1971 [73] Assignee Standard Oil Company Chicago, 111.

[54] CROP-DRYING OIL BURNER 12 Claims, 1 Drawing Fig.

[52] US. Cl 431/351, 431/174, 431/183 [51] Int. Cl F23d 15/00 [50] Field of Search 431/174, 175,182, 183, 187,188, 351, 354

[56] References Cited UNITED STATES PATENTS 2,806.516 9/1957 Brola 431/174 X Recirculating Stream 3,076,497 2/1963 Robb 431/183 X 3,266,549 8/1966 Wolfersperger 431/351 X 3,393,964 7/1968 Donnelly 431/351 X Primary Examiner-Carroll B. Dority, Jr. Attorneys-Arthur G. Gilkes, William T. McClain and John J.

Connors ABSTRACT: Disclosed is a crop-drying oil burner particularly adapted to be used outdoors when ambient temperatures are below about 45 F. This burner includes an inner cylindrical combustion chamber, and a concentric outer air chamber spaced from the inner chamber and including a spaced front plate which covers the open front end of the inner chamber. This front plate has a circular orifice therein which allows flame to shoot out of the inner chamber. High-velocity air is blown through the inner chamber and through the gap between the inner and outer chambers, sweeping across the front plates inside surface, keeping it free of carbon.

CROP-DRYING OIL BURNER BACKGROUND OF THE INVENTION U.S. application Ser. No. 788,696, entitled Crop Drying Oil Burner, "filed Dec. 27, 1968, in the names of Donald C. Walker, John Bachi, Jr., and Russell A. Hunt, Jr., discloses a direct-fired oil burner which can be used to dry grain. Because of the novel design of this burner, smoky oil combustion is eliminated so that the grain remains free of taste, odor, and color components. During outdoor field testing, this burners performance was found to be excellent so long as ambient temperatures were about 45 F. or above. At lower temperatures, however, carbon accumulated at the front end of the burner. This required that the burner be periodically shut down and cleaned. There was also some accumulation of carbon on the shield means which protect the fuel feeding and igniting means, but this carbon deposition was not too serious. Nevertheless, it would be desirable to eliminate it.

DESCRIPTION OF THE INVENTION I have improved the design of the crop-drying oil burner disclosed in Ser. No. 788,696 so that, despite cold ambient temperatures, carbon buildup is virtually eliminated. I found that carbon deposition is avoided if air is distributed across the surfaces of the burner which normally collect carbon. These airstreams, moving generally parallel to the surface being protected, prevent carbon buildup on these surfaces. It is also desirable to use a thick-walled combustion chamber, for example, about AII'lCII thick stainless steel. This thick-walled chamber better retains heat and more uniformly distributes it throughout the combustion chamber.

Since many of the features of the present invention will best be understood in light ofthe teaching in Ser. No. 788,696, I intend Ser. No. 788,696 to be incorporated by reference into the present application. The major elements of the oil burner disclosed in Ser. No. 788,696 are: (l) chamber means having front and rear openings which allow air to enter and leave the chamber means, said rear openings being sufficiently expansive to permit entry of enough air to guarantee smoke-free combustion and sufficiently restrictive to prohibit entry of excess air to guarantee against undue cooling which causes smoky shutdown, (2) means adjacent the rear opening for blowing air into said rear opening, through the chamber means, and out the front opening, (3) means coupled to the chamber means for establishing within the chamber means a vortex of swirling air, a laminarlike airstream which surrounds the vortex and moves from the rear opening towards the front opening, and a recirculating air stream which flows counter to the laminarlike airstream, and (4) means coupled to the chamber means for feeding oil into the vortex of swirling air and for igniting the oil-air mixture.

The improved crop-drying oil burner of my invention, in addition to the above elements, also includes means for directing air across inside burner surfaces which tend to accumulate carbon. This air directing means may include plate means spaced from the front opening of the chamber to allow an airstream to be directed across the plate means inside surface. The plate means has an opening therein which is about onehalf the diameter of the chamber. The air, moving generally parallel to the plates inside surface, prevents carbon buildup on this inside surface. Thus carbon deposition is prevented or retarded.

The oil burner of Ser. No. 788,696 may also include shield means surrounding the oil-feeding and igniting means to protect against overheating of these means and prevent buildup of carbon on the igniting means. Carbon, however, tends to accumulate on the outside surface of the shield means. I have found that, when this surface is curved inwardly towards the center of the chamber and air is directed across this curved surface, carbon deposition thereon is eliminated.

DESCRIPTION OF PREFERRED EMBODIMENT FIGURE, which is a schematic cross-sectional view of my improved burner 10, shows the major burner componentshousing 12, inner combustion chamber 14 and outer air chamber 16, both attached to housing 12, and air moving means 18 shown schematically. Details of air moving means 18 are illustrated in U.S. Ser. No. 788,696.

Inner chamber 14 is welded at junctions 20 to front 22 of housing 12, and it is preferably made of /4-inch thick stainless steel. Because of the improved heat retention and distribution provided by using such thick-walled stainless steel, complete vaporization of oil within chamber 14 is insured. Chamber 14 is essentially a hollow cylinder having an open front end 24 and partially closed rear end 26 including rear plate 28.

The details of rear plate 28 are illustrated in U.S. Ser. No. 788,696; however, its more important features will be mentioned here. At the periphery of plate 28 are a plurality ofconcentric apertures 30, and between the periphery of plate 28 and the center of plate 28 are a plurality of radially extending slits 32. Adjacent each slit 32 is a pitch blade 34 which causes air entering inner chamber 14 to swirl about and form a vortex within the inner chamber. The size and number of apertures 30 and slits 32 is controlled so that the ratio of air entering chamber 14 through the apertures to air entering chamber 14 through the slits is about 1:1. Mounted at the center of rear plate 28 is fuel feeding and igniting means 36, including nozzles 38 and electrodes 40. Nozzles 38 are aligned 5 inward to direct oil towards the center section of chamber 16. Shield means 41, in the form of a frustoconical member welded to rear plate 28, protects fuel feeding and igniting means 36 against overheating and prevents carbon deposition on electrodes 40.

If the shield means is in accordance with the design shown in U.S. Ser. No. 788,696, carbon tends to deposit on the outer surface of the shield means when ambient temperature is below about 45 F. I have found that this carbon deposition can be eliminated, or at least drastically reduced, if shield means 41 is contoured as shown in the FIGURE. Locating central apertures 30a closely proximate to the points of attachment 42 of shield means 41 to rear plate 28, and curving exposed surface 44 of shield means 41 inwardly towards the center of inner chamber 14, constitutes one of the improvements of this invention. Air rushing into inner chamber 14 tends to attach itself to curved surface 44 and flow across this surface, keeping it free ofcarbon.

To prevent buildup of carbon on the inside surfaces of inner chamber 14, several modifications may be made in the basic burner design of U.S. Ser. No. 788,696. Of course, these modifications are only expedient if ambient temperature is below about 45 F. One of these modifications is locating peripheral apertures 30b closely proximate to the points of attachment 48 between rear plate 28 and rear end 26 of chamber 14. Thus, air is directed across the rear inside surface 50 of inner chamber 14, keeping it free of carbon.

Another modification, and by far the most important, is the use of outer air chamber 16. Outer chamber 16 is cylindrical, and it is concentric with and spaced from the inner chamber 14 so that there is a gap 52 (for example, about one-half inch) between outer surface 54 of chamber 14 and inner surface 56 of chamber 16. Rear end 58 of outer chamber 16 is welded to front 22 of housing 12, but there are a plurality of openings 60 in the housing to enable air to flow through gap 52. Front end 62 of chamber 16 tapers inwardly to form front plate 64 which covers open front end 24 of inner chamber 14. Front plate 64 turns outwardly to form lip 66 which defines a circular orifice 68 within the front plate. This orifice 68 has a diameter equal to about one-third to about two-thirds, preferably about onehalf, the diameter of inner chamber 14. The dimensions of burner 10 should be such that this ratio of inner chamber diameter to inner chamber length to orifice diameter is about 2:2-311, preferably about 222.5:1. The contoured shape of plate 64, especially lip 66, retards warping, which occasionally occurs if the front plate is perpendicular to the burner sidewalls. Moreover, front plate 64 is spaced from front end 24 of inner chamber 14 so that, between front plate 64 and front end 24, there is a gap 70 (for example, about one-eighth inch). Gap 70 permits air to flow across inside surface 72 of plate 64, and this air flow prevents the buildup of carbon on surface 72.

In operation, a high-velocity blast of air from air-moving means 18 passes through diffusion screen 74 within housing 12 into burner 10 via openings 60, apertures 30, and slits 32. Simultaneously nozzles 38 inject oil into the central section of inner chamber M and a spark jumps between electrodes 40 to ignite the oil and air mixture within chamber 14. This fills the forward end (about forward one-half) of chamber 14 with flame 76 that shoots out orifice 68. At the same time, air passes through gap 52 between chamber 14 and 16 and through gap 70 between front plate 64 and front end 24, sweeping across inside surface 72 to prevent carbon buildup on plate 64. Air also passes over curved surface 44 of shield means 41 and rear inside chamber surface 50, sweeping across these surfaces to prevent carbon buildup thereon.

The rear plate 28 establishes within inner chamber 14 a vortex of swirling air and a laminarlike airstream which surrounds the vortex and moves from rear end 26 to front end 24, and front plate 64 establishes recirculating airstream directed to flow counter to the laminarlike airstream. Such air flow promotes complete vaporization of the oil, and therefore clean burning. The apertures 30 and slits 32 are sufficiently expansive to permit entry of enough air to guarantee smokefree combustion and sufficiently restrictive to prohibit entry of excess air to guarantee against undue cooling of chamber M, which causes smoky shutdown.

The above features of burner Iincluding the relative size and shape of chambers M and 16, relative size and shape of apertures 30, slits 32, orifice 68, and air flow through the inner and outer chambers-contribute to a greater or lesser degree to the improved operation of crop drying oil burner of my invention so that carbon buildup within chamber 14 is virtually eliminated.

lclaim:

1. In an oil burner including chamber means having front and rear openings which allow air to enter and leave said chamber means, said rear opening being sufficiently expansive to permit entry of enough air to guarantee smoke-free com bustion and sufficiently restrictive to prohibit entry of excess air to guarantee against undue cooling of the chamber means causing smoky shutdown, means adjacent the rear opening for blowing air into said rear opening, through the chamber means, and out the front opening, means coupled to the chamber means for establishing within said chamber means a vortex of swirling air, a laminarlike airstream which surrounds said vortex and moves from the rear opening towards the front opening, and a recirculating airstream which flows counter to the laminarlike airstream, and means coupled to the chamber means for feeding oil into the vortex of swirling air and for igniting the oil-air mixture;

the improvement wherein the means for establishing a recirculating airstream includes plate means having a central orifice therein and an inside surface spaced from the front opening of the chamber, and wherein the burner additionally includes means for directing air across said plates inside surface.

2. The improved burner defined in claim 1 wherein the chamber has a cylindrical configuration and the orifice in said plate is circular, having a diameter equal to from about onethird to about two-thirds the diameter of the chamber.

3. The improved burner defined in claim 2 wherein the ratio of chamber diameter to chamber length to orifice diameter is about 2:2--3:l preferably about 2:2.511.

4. The improved burner defined in claim 1 including shield means which surrounds said oil feeding and igniting means and prevents overheating of these means and buildup of carbon and the like on the igniting means, and means for directing air across the outer surface of the shield means.

5. The improved burner defined in claim 1 wherein the oilfeeding means includes a plurality of nozzles aligned to direct oil towards the central section of the chamber means.

6. The improved burner defined in claim 1 wherein the chamber is made of thick walled stainless steel.

7. An oil burner comprising:

An inner hollow cylindrical combustion chamber having an open front end and a rear end closed off by a rear plate having therein aperture means adjacent the periphery of the rear plate and radially extending slit means between said periphery and the center of the rear plate, and having thereon blade means adjacent the slit means which cause air moving into and through the chamber to swirl about and mix with any oil being fed into the chamber;

an outer hollow cylindrical air chamber concentric with and spaced from the first chamber so that between the outside of the first chamber and the inside of the second chamber there is a gap, said outer chamber having open front and rear ends and including a front plate which covers the open front end of the first chamber and has therein a centrally located circular orifice having a diameter of from about one-third to about two-thirds the diameter of the first chamber, said front plate being spaced from the front end of the first chamber so that air flowing through said gap passes across the inside of said front plate;

means adjacent said rear plate for moving air through the gap and through the aperture means and slit means into the chambers and out said orifice; and

means mounted centrally within said rear plate for feeding oil into the chamber and for igniting the oil-air mixture.

8. The burner defined in claim 7 wherein the ratio of inner chamber diameter to inner chamber length to orifice diameter is about 2:23: 1 preferably about 212.5:1.

9. The burner defined in claim 8 wherein the ratio of air entering the inner chamber through said aperture means to air entering the inner chamber through said slit means is about l:l.

10. The burner defined in claim 7 wherein a frustoconical shield, attached to the rear plate, surrounds said fuel feeding and igniting means and protects against overheating of these means and prevents buildup of carbon and the like on the igniting means, said shield having a surface which is curved inwardly towards the center of the inner chamber, and at least some of said aperture means are located in close proximity to the point of attachment between the shield and rear plate so that an airstream is directed across the curved surface of the shield.

11. The burner defined in claim 7 wherein the front plate is tapered to form an outwardly turned lip which defines the perimeter of the orifice.

12. The burner defined in claim 7 wherein the inner chamber is made of thick-walled stainless steel. 

1. In an oil burner including chamber means having front and rear openings which allow air to enter and leave said chamber means, said rear opening being sUfficiently expansive to permit entry of enough air to guarantee smoke-free combustion and sufficiently restrictive to prohibit entry of excess air to guarantee against undue cooling of the chamber means causing smoky shutdown, means adjacent the rear opening for blowing air into said rear opening, through the chamber means, and out the front opening, means coupled to the chamber means for establishing within said chamber means a vortex of swirling air, a laminarlike airstream which surrounds said vortex and moves from the rear opening towards the front opening, and a recirculating airstream which flows counter to the laminarlike airstream, and means coupled to the chamber means for feeding oil into the vortex of swirling air and for igniting the oil-air mixture; the improvement wherein the means for establishing a recirculating airstream includes plate means having a central orifice therein and an inside surface spaced from the front opening of the chamber, and wherein the burner additionally includes means for directing air across said plate''s inside surface.
 2. The improved burner defined in claim 1 wherein the chamber has a cylindrical configuration and the orifice in said plate is circular, having a diameter equal to from about one-third to about two-thirds the diameter of the chamber.
 3. The improved burner defined in claim 2 wherein the ratio of chamber diameter to chamber length to orifice diameter is about 2:2-3:1, preferably about 2:2.5:1.
 4. The improved burner defined in claim 1 including shield means which surrounds said oil feeding and igniting means and prevents overheating of these means and buildup of carbon and the like on the igniting means, and means for directing air across the outer surface of the shield means.
 5. The improved burner defined in claim 1 wherein the oil-feeding means includes a plurality of nozzles aligned to direct oil towards the central section of the chamber means.
 6. The improved burner defined in claim 1 wherein the chamber is made of thick-walled stainless steel.
 7. An oil burner comprising: An inner hollow cylindrical combustion chamber having an open front end and a rear end closed off by a rear plate having therein aperture means adjacent the periphery of the rear plate and radially extending slit means between said periphery and the center of the rear plate, and having thereon blade means adjacent the slit means which cause air moving into and through the chamber to swirl about and mix with any oil being fed into the chamber; an outer hollow cylindrical air chamber concentric with and spaced from the first chamber so that between the outside of the first chamber and the inside of the second chamber there is a gap, said outer chamber having open front and rear ends and including a front plate which covers the open front end of the first chamber and has therein a centrally located circular orifice having a diameter of from about one-third to about two-thirds the diameter of the first chamber, said front plate being spaced from the front end of the first chamber so that air flowing through said gap passes across the inside of said front plate; means adjacent said rear plate for moving air through the gap and through the aperture means and slit means into the chambers and out said orifice; and means mounted centrally within said rear plate for feeding oil into the chamber and for igniting the oil-air mixture.
 8. The burner defined in claim 7 wherein the ratio of inner chamber diameter to inner chamber length to orifice diameter is about 2:2-3:1, preferably about 2:2.5:1.
 9. The burner defined in claim 8 wherein the ratio of air entering the inner chamber through said aperture means to air entering the inner chamber through said slit means is about 1:1.
 10. The burner defined in claim 7 wherein a frustoconical shield, attached to the rear plate, surrounds said fuel feeding and igniting means and protects against overheating of these meanS and prevents buildup of carbon and the like on the igniting means, said shield having a surface which is curved inwardly towards the center of the inner chamber, and at least some of said aperture means are located in close proximity to the point of attachment between the shield and rear plate so that an airstream is directed across the curved surface of the shield.
 11. The burner defined in claim 7 wherein the front plate is tapered to form an outwardly turned lip which defines the perimeter of the orifice.
 12. The burner defined in claim 7 wherein the inner chamber is made of thick-walled stainless steel. 